Alkyd resins in organic solvent medium, otherwise known as solvent-based media, are resins that have been well known for a long time by those skilled in the art, and are generally used in decorative and industrial coatings and paint formulations. In response to questions of ease of use, odor and toxicity, specific alkyd resin emulsions have been developed and marketed for about twenty years, with advantageous performance levels in terms of gloss, drying, appearance/color, stability and odor. A conventional implementation technique solution, used for forming alkyd resin emulsions that are stable over time, consists in using a combination of a nonionic surfactant with an anionic surfactant as described in WO 2008/076 360.
Despite these improvements, certain parameters and performance qualities remain to be improved, such as the resistance to yellowing, the resistance to blocking, the hardness and the drying.
In the field of coatings, in particular for decorative applications, commercial urethane-treated alkyd resin dispersions exist, for instance WorleeSol® E 150 W supplied by Worlee, which are known for rapid development of hardness and for affording saving in terms of initial drying in paints composed of alkyd resin dispersions, optionally mixed with other aqueous dispersions such as latices. However, these urethane-treated dispersions are subject to problems of development of yellowing over time that are more pronounced than in the case of alkyd resin and acrylic dispersions. Furthermore, the levels of gloss are reduced when compared with alkyd resin dispersions or (worse) acrylic dispersions, which is why (high-quality) gloss paint formulations nowadays contain a small proportion of urethane-treated dispersion. In parallel, there is a need to further increase the level of physical drying, in particular the initial drying (drying during the first hours after application), and if possible, without the need for a toxic siccative agent such as cobalt or lead derivatives.
Moreover, the environmental constraints and the challenges linked to sustainable development increase the need for linked aqueous resins and dispersions, which have a reduced content of VOC produced with starting materials of renewable (or non-fossil) origin.
The resin of the invention allows the preparation of aqueous polyurethane dispersions based on fatty polyesters which satisfy these needs or overcome the drawbacks of the mentioned known dispersions.